TOWARDS A HEALTHIER APPLE - CHEMICAL CHARACTERIZATION OF AN APPLE GENE BANK

Apple cultivars in a Swedish gene bank were evaluated for phenolic compounds and for the Mal d 1 allergen. The analysed cultivars differed considerably in content of total polyphenols determined in fruit skin ranging from 5710 to 26,180 µg GAE/g dm (GAE=gallic acid equivalents) with an average of 13,950 µg GAE/g dm. They also varied in content of the major phenolic compounds (range in µg/g dm): quercetin-3-rutinoside, 0–720; quercetin-3-galactoside, 60–2290; quercetin-3-glucoside, 20–1770; quercetin-3-xyloside, 80–970; quercetin-3-arabinoside, 180–2160; quercetin-3-rhamnoside, 30–3440; catechin, 0–1630; procyanidin B2, 100–4380; epicatechin, 60–3700; phloridzin, 30–2840; and chlorogenic acid, 15–3590. The average content of phenols, the range in content of each phenolic compound, and the coefficient of variation was consistent between years in 99 cultivars analysed in two successive years. The correlation coefficient was also high between years for each of the phenolic compounds studied. The amount of Mal d 1 was determined by Western analysis in freshly harvested fruits and in fruits stored for 2–8 weeks. Apple skin had a higher concentration than the fruit flesh in freshly harvested fruits. During storage, the amount of allergens increased both in the skin and in the fruit flesh. Considerable differences were found between cultivars in the initial amount of Mal d 1 and in the development during storage. Preliminary results also suggest an influence from time of harvest and storage conditions. Establishment of DNA marker profiles for the chemically investigated cultivars with RAPD and SSR loci enabled unambiguous identification of the plant material as well as estimation of genetic relatedness among genotypes.